Squatinactis

Squatinactis Temporal range: Serpukhovian to Namurian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii Zangerl, 1981
Order:	†Squatinactiformes Cappetta et al., 1993
Family:	†Squatinactidae Lund and Zangerl, 1974
Genus:	†Squatinactis Lund and Zangerl, 1974
Species
S. caudispinatus Lund and Zangerl, 1974 (type) S. glabrum Ginter, 1999 S. multicuspidatus Ivanov et al., 2023

Squatinactis is a genus of extinct elasmobranch chondrichthyan known from the Carboniferous aged Bear Gulch Limestone in Montana.^[1] This fish was discovered in 1974 by Richard Lund.^[1] The type specimen, named CMNH 46133, consists of a brain case, poorly preserved jaws and gills, a pectoral fin, and a partial vertebral axis.^[1] This creatures most startling feature were its broad pectoral fins which resembled those of stingrays and angel sharks (Squatina).^[1] The holotype specimen has about 15 teeth in its jaw.^[1] This creature is named after the angel shark.^[1] Remains found in the South Urals of Russia and the Eyam Limestone of Derbyshire, England, have been tentatively identified as those belonging to S. caudispinatus.^[2][3]

Description

Squatinactis had a flattened body with a set of large pectoral fins. This fish was vaguely similar to today's stingrays and angel sharks. The fins were oddly pointed forward, with a length of around two feet long. It also had a long, whip-like tail with a spine (a feature analogous to some rays) that was actually a modified, secondary dorsal fin.^[1] The snout was short and the wide mouth was equipped with a series of long conical cladodont-shaped teeth. The body was covered in a few placoid scales, but most of the surface was bare.^[1]

Classification

Because of the bizarre nature of Squatinactis, it is somewhat difficult to classify. In the original study conducted in 1974, Lund noted that the teeth of this fish are Cladodont is design,^[1] however the term "cladodont" is used to describe many Paleozoic chondrichthyans based on their teeth and not phylogeny (including Cladoselache, Ctenacanthus, and Dracopristis). This fish is currently classified within the Elasmobranchii, more specially in its own grouping, the Squatinactiformes.^[4]

Ecology

This fish was probably a benthic predator; it probably lived half-buried in the sand and suddenly emerged to throw itself against the prey swimming nearby. The wing-like fins and long tail were most likely useful for propulsion from the seabed. The flattened body plan is typical of bottom-dwelling predators, and is known in a large number of cartilaginous fish, both extinct and extant.

References

• v
• t
• e

Total group Chondrichthyes (including "acanthodians")

Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Infraphylum: Gnathostomata
Gnathostomata see Gnathostomata Chondrichthyes see below↓

Chondrichthyes

Chondrichthyes †Cassidiceps †Euthacanthus †Latviacanthus †Ramirosuarezia? †Sinacanthidae Hunanacanthus Neosinacanthus Sinacanthus Tarimacanthus †"Ischnacanthiformes" Acanthospina Campylodus Granulacanthus Machaeracanthus? Onchus Serradentus Acritolepidae Acritolepis Monospina Nerepisacanthus Pechoralepis Ischnacanthidae Arcticacanthus Arenaceacanthus Atopacanthus Bracteatacanthus Cacheacanthus Erymnacanthus Euryacanthus Gomphonchus Grenfellacanthus Ischnacanthus Marsdenius? Persacanthus Plectrodus Rockycampacanthus Rohonilepis Taemasacanthus Tricuspicanthus Xylacanthus Podoliacanthidae Drygantacanthus Kasperacanthus Podoliacanthus Poracanthodidae Gomphonchoporus Machaeraporus Obruchevacanthus? Poracanthodes Radioporacanthodes Taimyrolepis Trundlelepis Zemlyacanthus †Diplacanthiformes Bryantonchus Culmacanthus? Devononchus Striacanthus Tetanopsyrus Uraniacanthus Diplacanthidae Diplacanthus Milesacanthus Ptychodictyon Rhadinacanthus †Acanthodiformes Halimacanthodes Howittacanthus Acanthodidae Acanthodes Acanthodopsis Traquairichthys Cheiracanthidae Cheiracanthus Fallodentus Ginkgolepis Homalacanthus Markacanthus Mesacanthidae Lodeacanthus Melanoacanthus Mesacanthus Orcadacanthus Promesacanthus Teneracanthus? Triazeugacanthus "Climatiiformes" and related taxa †Brochoadmones †Dobunnacanthus †Fanjingshania? †Kathemacanthus †Lupopsyroides †Lupopsyrus †Obtusacanthus †Paucicanthus †Ptomacanthus †Qianodus? †Vernicomacanthus †Climatiidae Brachyacanthus Climatius Erriwacanthus Nodocosta? Parexus Sevyacanthus †Gyracanthidae Aganacanthus? Ankylacanthus Gyracanthides Gyracanthus Oracanthus? "Conventionally defined chondrichthyans" see below↓

"Conventionally defined chondrichthyans"
"Conventionally defined chondrichthyans" †Carcharopsis †Celtiberina †Gladbachus? †Gogoselachus †Karksiodus †Leonodus †Plesioselachus †Polymerolepis †Protodus †Samarodus †Shenacanthus? †Squatinactis †Antarctilamnidae Antarctilamna Wellerodus? †Mcmurdodontidae Maiseyodus Mcmurdodus †Pucapampellidae Gydoselache Pucapampella †Omalodontiformes Siberiodus Aztecodontidae Aztecodus Manberodus Omalodontidae Doliodus? Omalodus Portalodus †"Ctenacanthiformes" Neosaivodus Saivodus Sculptospina Tamiobatis Ctenacanthidae Arduodens? Cladodoides Cladodus Ctenacanthus Goodrichthys Natarapax? Troglocladodus Heslerodidae Avonacanthus Bythiacanthus Dracopristis Glencartius Glikmanius Heslerodoides Heslerodus Kaibabvenator Nanoskalmae †Jalodontidae Adamantina Isacrodus Jalodus Keuperodus Texasodus †Phoebodontidae Diademodus? Phoebodus Thrinacodus †Symmoriiformes Dwykaselachus Ferromirum Kawichthys Kungurodus? Maiseyacanthus Cladoselachidae? Cladoselache Maghriboselache Falcatidae Cosmoselachus Cretacladoides? Damocles Denaea Falcatus Ozarcus? Stethacanthulus Symmoriidae Akmonistion Cobelodus Crioselache? Stethacanthus Symmorium †Bransonelliformes Barbclabornia Bransonella †Xenacanthiformes Orthacanthus Tikiodontus Diplodoselachidae Decentrodus Diplodoselache Hagenoselache Hokomata Lebachacanthus Taquaralodus Xenacanthidae Mooreodontus Plicatodus Triodus Wurdigneria Xenacanthus Crown-Chondrichthyes Holocephali Elasmobranchii

Incertae sedis scale-based taxa

†Altholepidiformes? Altholepis Tezakia †Elegestolepidida? Kannathalepis Elegestolepididae Deltalepis Elegestolepis Ellesmereia †Mongolepidida? Solinalepis Mongolepididae Mongolepis Rongolepis Sodolepis Taklamakanolepis Teslepis Shiqianolepidae Chenolepis Shiqianolepis Tielikewatielepis Xiaohaizilepis Xinjiangichthys †Tchunacanthidae Fecundosquama Lenacanthus Tchunacanthus †Vesperaliidae Acanthacanthus Vesperalia Others †Canyonlepis? †Frigorilepis? †Funicristata †Gualepis †Ivanelepis †Jolepis †Karksilepis †Lunalepis †Nobilesquama †Nostolepis †Nostovicina †Ohiolepis †Seretolepis †Tuvalepis †Wellingtonella? †Yuanolepis

• Category

This article about a prehistoric cartilaginous fish is a stub. You can help Wikipedia by expanding it.

• v
• t
• e